This invention generally relates to a light dimmer control system, and more particularly, to a dimmer control system employing a master unit in communication with one or more remote units.
Dimmer lighting and control systems are widely used in indoor lighting to provide a softer feel and more controllable illumination experience as compared to on/off lighting. Prior dimmer lighting systems have employed dimmer switch controls that include an on/off switch and an up/down power control, master unit and remote units, and microprocessor control for various power-up, power-down and fade in/out functions. Rather than use a variable resistor type rheostat which wastes power and generates heat at low illumination levels, modern dimming systems employ phase regulation, in which the power circuit is switched on at a time delay following a zero-crossing of the AC sine wave input until the end of each half cycle in order to supply a variable level of power to the lighting load.
However, prior multi-location dimmer control systems have various shortcomings and problems in operation. In systems that employ master and remote units, the remote units are xe2x80x9cdumbxe2x80x9d boxes that simply have on/off and up/down switches but do not indicate the lighting status of the system. Attempts to provide two-way communication functions between the master and remote units would impose added costs and difficulties in outfitting the remote units with power sources and the capability to communicate with the master unit.
For example, a typical prior art multi-location dimmer (shown in FIG. 5) consists of a fully functional master unit and a number of remote units (1, . . . n), where the remote units are connected in parallel with each other between a xe2x80x9cswitched hotxe2x80x9d line of the master unit and a xe2x80x9cTravelerxe2x80x9d or xe2x80x9cControlxe2x80x9d line of the master unit. The remote units communicate to the master unit by sending a portion of the output current on the Traveler line to the control input of the master unit. To transmit three commands (Up, Down, and Toggle On/Off), positive, negative and alternating waveforms are used. These remote units require no power in normal operation, and cannot display the level of light setting. To display the light setting level, the remote units would require power and two-way communication means. The task of supplying power to the remote units is quite complicated, as every remote would need some current to operate. With the remote units connected in parallel, total current drawn from the control terminal of the master unit unit would be proportional to the number of remote units connected to the system. When this current reaches a certain level, the lamp load may start glowing (showing illumination) when it is supposed to be in the Off condition. Also the power supply size needed would increase in proportion to the maximum number of remote units that could be connected to the system.
For a multi-location dimmer that supplies power to the remote units, there may be a problem that the internal dimmer""s power supply could create an audible noise in the load when the load is Off, which otherwise would be masked when the load is On. This power supply may also generate waste heat.
It is also known in prior dimmer control systems to use control memory to restore the illumination level to the same level as when it was last powered off, as a user often sets the illumination level to a desired comfort level and wants the same level when turning the light system back on again. However, the use of a separate latch device is limited to memorizing only whether the load was on or off, and the use of ongoing memory storage of the current power level requires use of a memory component capable of extremely high usage of read/write cycles, which imposes an added cost.
In accordance with the present invention, a dimmer control system is provided with a communication control loop that connects a master unit in series with the source and the load, and a plurality of remote units in series with each other between the xe2x80x9cSwitched Hotxe2x80x9d line and the xe2x80x9cTravelerxe2x80x9d or xe2x80x9cControlxe2x80x9d line of the master unit, and the communication control loop is superimposed on the dimmer load line in a manner that allows two-way communication between the master unit and the remote units without any effect from the dimmer load current on the communication. Communication messages from the master unit to the remote units are encoded in loop current fluctuations that are decoded by the remote units, and communication messages from any remote to the master unit are encoded in loop voltage fluctuations that are decoded by the master unit.
In a preferred embodiment of the invention, the communication control loop connects the master unit""s control circuit in series with the respective remote units so as to minimize the current requirements and the required power supply size. The master unit uses a switched power supply during normal operation. The communication loop is hosted and synchronized by the master unit, and the communication messages are transmitted close to the timing of the input line voltage zero crossings, i.e., at the beginning of each half-cycle of input line voltage. The master unit""s power circuit provides an output rail voltage equal to the sum of the total control loop voltage drop attributable to the series-connected control circuits of the remote units and a fixed reference voltage. The reference voltage for the power supply is tied to the control loop voltage drop, thus generating minimum heat regardless of the number of remote units in the loop.
As a further aspect of the present invention, the master unit""s power circuit maintains its switched power supply in tandem with a capacitive power supply. The switched power supply is used during normal LOAD ON conditions, whereas the capacitive power supply is used to continue to supply power to the system during LOAD OFF conditions, when the switched power supply is switched off in order to avoid acoustic noise (hum) in the load. The switched power supply with floating reference voltage powers the system during normal LOAD ON conditions in order to avoid the heat generation that would be incurred by otherwise using a capacitive power supply.
As another aspect of the invention, the master unit""s control circuit includes a non-volatile memory that is written with system status information when a POWER OFF condition is detected. When a POWER ON condition is restored, the stored system status information is used to restore the operation of the dimmer control system to where it was before the POWER OFF condition. In the preferred embodiment, a POWER OFF condition (power interruption) is detected when two consecutive zero crossings are not detected by the microprocessor, and the system status information temporarily stored in its RAM is recorded in the non-volatile memory, using the energy accumulated in a reservoir capacitor to power the recording process.
As yet another aspect of the invention, the master and remote units have a physical configuration in which an ON/OFF switch component is hinged for slight actuator ON/OFF movement on a hinge axis along one lateral side of the unit""s frame, and a system status display is formed by an array of light indicators comprising a row of indicator lenses arranged in the surface of the ON/OFF switch component and aligned in close proximity in parallel with the hinge axis and optically connected by light pipes to respective LEDs on the control unit""s control circuit board, wherein any slight displacement of the light pipes caused by actuator movement of the ON/OFF switch component can be minimized to avoid light fluctuations in the display of the indicator lenses.
Other objects, features, and advantages of the present invention will be explained in the following detailed description of the invention having reference to the appended drawings.